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Chromosomal Deletion Syndromes

By

Nina N. Powell-Hamilton

, MD, Sidney Kimmel Medical College at Thomas Jefferson University

Last full review/revision Jun 2020| Content last modified Jun 2020
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Chromosomal deletion syndromes result from loss of parts of chromosomes. They may cause severe congenital anomalies and significant intellectual and physical disability. Specific chromosomal deletion syndromes are less likely to be suspected prenatally but may be incidentally discovered at that time if karyotyping is done for other reasons. Postnatal diagnosis is suspected by clinical appearance and is confirmed by karyotyping, if the deletion is relatively large, or by other cytogenetic techniques such as fluorescent in situ hybridization or microarray analysis.

5p- syndrome (5p minus syndrome or cri-du-chat syndrome)

Deletion of the end of the short arm of chromosome 5 (5p minus, usually paternal) is characterized by a high-pitched, mewing cry, closely resembling the cry of a kitten, which is typically heard in the immediate neonatal period, lasts several weeks, and then disappears. However, not all affected neonates have this unusual cry. Affected neonates are hypotonic and have low birth weight, microcephaly Microcephaly Microcephaly is a head circumference 2 standard deviations below the mean for age. (See also Introduction to Congenital Craniofacial and Musculoskeletal Disorders and Overview of Congenital... read more Microcephaly , a round face with wide-set eyes, downward slanting of the palpebral fissures (with or without epicanthal folds), strabismus Strabismus Strabismus is misalignment of the eyes, which causes deviation from the parallelism of normal gaze. Diagnosis is clinical, including observation of the corneal light reflex and use of a cover... read more Strabismus , and a broad-based nose. The ears are low-set, abnormally shaped, and frequently have narrow external auditory canals and preauricular tags. Syndactyly Syndactyly Congenital limb defects involve missing, incomplete, supernumerary, or abnormally developed limbs present at birth. (See also Introduction to Congenital Craniofacial and Musculoskeletal Disorders... read more Syndactyly , hypertelorism Hypertelorism Eyes can be absent, deformed, or incompletely developed at birth. (See also Introduction to Congenital Craniofacial and Musculoskeletal Disorders and Overview of Congenital Craniofacial Abnormalities... read more Hypertelorism , and cardiac anomalies Overview of Congenital Cardiovascular Anomalies Congenital heart disease is the most common congenital anomaly, occurring in almost 1% of live births (1). Among birth defects, congenital heart disease is the leading cause of infant mortality... read more Overview of Congenital Cardiovascular Anomalies occur often. Mental and physical development is markedly retarded. Many affected children survive into adulthood but have significant disability.

4p- syndrome (4p minus syndrome or Wolf-Hirschhorn syndrome)

Deletion of the short arm of chromosome 4 (4p) results in variable intellectual disability Intellectual Disability Intellectual disability is characterized by significantly subaverage intellectual functioning (often expressed as an intelligence quotient 70 to 75) combined with limitations of adaptive functioning... read more ; individuals with larger deletions are usually more severely affected. Manifestations also may include epilepsy, a broad or beaked nose, midline scalp defects, ptosis and colobomas Coloboma Eyes can be absent, deformed, or incompletely developed at birth. (See also Introduction to Congenital Craniofacial and Musculoskeletal Disorders and Overview of Congenital Craniofacial Abnormalities... read more Coloboma , cleft palate Cleft Lip and Cleft Palate Cleft lip, cleft lip and palate, and isolated cleft palate, are collectively termed oral clefts (OCs). OCs are the most common congenital anomalies of the head and the neck with a total prevalence... read more Cleft Lip and Cleft Palate , delayed bone development, and, in boys, hypospadias Hypospadias Congenital anomalies of the urethra in boys usually involve anatomic abnormalities of the penis and vice versa. In girls, urethral anomalies may exist without other external genital abnormalities... read more Hypospadias and cryptorchidism Cryptorchidism Cryptorchidism is failure of one or both testes to descend into the scrotum; in younger children, it is typically accompanied by inguinal hernia. Diagnosis is by testicular examination, sometimes... read more Cryptorchidism . Some patients with Wolf-Hirschhorn syndrome also have immune deficiency. Many affected children die during infancy; those who survive into their 20s often have severe disability.

Subtelomeric deletions

These deletions may be visible on karyotyping but are also sometimes small and submicroscopic and may occur at either telomere (the end of a chromosome). Phenotypic changes may be subtle. Subtelomeric deletions may be associated with nonspecific intellectual disability and mildly dysmorphic features as well as multiple congenital anomalies.

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